A study in the university of ST. Andrews in the unisted kingdom groups students into five group. The students in each of the five groups learned to produce Oldtown tools (a form of ancient tool) in different ways. In each group, the learner became the teacher in the next round. In this fashion, the research team created five different '' chain of transmission'' of Oldtown toolmakers. The groups that taught with gestures doubled and the growth using verbal teaching quadrupled the likelihood that the tool was properly recreated. Based on the information provided, which basic trend in hominid evolution, was being evaluated through the creation of these tools?